Conductivity control of as-grown branched indium tin oxide nanowire networks

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DOIResolve DOI: http://doi.org/10.1088/0957-4484/25/3/035701
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TypeArticle
Journal titleNanotechnology
ISSN0957-4484
Volume25
Issue3
Article number35701
Pages19; # of pages: 9
Subjectbranched nanowires; nanowires; indium tin oxide; Hz time-domain spectroscopy; conductivity
AbstractBranched indium tin oxide (ITO) nanowire networks are promising candidates for transparent conductive oxide applications, such as optoelectronic electrodes, due to their high porosity. However, these branched networks also present new challenges in assessing conductivity. Conventional four-point probe techniques cannot separate the effect of porosity on the long-range conductivity from the intrinsic material conductivity. Here we compare the average nanoscale conductivity within the film measured by terahertz time-domain spectroscopy (THz-TDS) to the film conductivity measured by four-point probe in a branched ITO nanowire network. Both techniques report conductivity increases with deposition flux rate from 0.5 to 3.0 nm s-1, achieving a maximum of ∼10 (Ω cm)-1. Modeling the THz-TDS conductivity data using the Drude-Smith model allows us to distinguish between conductivity increases resulting from morphological changes and those resulting from the intrinsic properties of the ITO. In particular, the intrinsic material conductivity within the nanowires can be extracted, and is found to reach a maximum of ∼3000 (Ω cm)-1, comparable to bulk ITO. To determine the mechanism responsible for increasing conductivity with flux rate, we characterize dopant concentration and morphological changes (i.e., to branching behavior, nanowire diameter and nucleation layers). We propose that changes in the electron density, primarily due to changes in O-vacancy concentration at different flux rates, are responsible for the observed conductivity increase. This understanding will assist balancing structural and conductivity requirements in applications of transparent conductive oxide networks.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); Security and Disruptive Technologies
Peer reviewedYes
NPARC number21273052
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Record identifiere63703ed-cbc4-4c5f-859c-de745ccef0f3
Record created2014-12-10
Record modified2016-05-09
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